1. Field of the Invention
The present invention relates to an image forming apparatus, a method of controlling the image forming apparatus, and a storage medium, and more particularly to an image forming apparatus that performs image formation capable of generating a print product in which a plurality of different sheets are mixed, a method of controlling the image forming apparatus, and a storage medium.
2. Description of the Related Art
Conventionally, in printing using tab sheets set in a sheet feeding cassette in an image forming apparatus, there has been known a technique for discharging surplus tab sheets outside the image forming apparatus after printing (see e.g. Japanese Patent Laid-Open Publication No. 2002-003063).
For example, one set of tab sheets is formed by a plurality of tab sheets. For example, one set of tab sheets including five tabs is formed by five sheets, and one set of tab sheets including three tabs is formed by three sheets. There has been generally used a technique in which assuming, for example, that three sheets out of a set of five tab sheets are used in one print job, two surplus tab sheets remain unused, and in such a case, the two surplus tab sheets are discharged out of the image forming apparatus after printing.
Although not limited to tab sheets, it is also general that when tab sheets are used again in the same or different job, sheet feeding is executed from the same sheet feeding cassette in which tab sheets are set.
However, if a plurality of sets of tab sheets are used in one print job, the productivity of the image forming apparatus is lowered.
For example, when a plurality of copies of a document are printed, surplus tab sheets in each copy are discharged out of the image forming apparatus, and tab sheets are continuously fed from the same sheet feeding cassette for all of the copies, and hence a ratio of time required to discharge surplus tab sheets to time required to obtain print products for the print job is large.
Next, a detailed description is given of a reason for such lowering of the productivity in generating print products due to discharge of surplus tab sheets.
In the above-mentioned conventional image forming apparatus, the temperature of a fixing device optimum for sheets is different depending on a sheet type, and hence whenever the sheet type is changed, the temperature of the fixing device is adjusted, and it takes time to achieve the temperature adjustment. After discharging the surplus tab sheets out of the apparatus as well, it requires time to adjust the temperature of the fixing device to a temperature optimum for normal sheets. However, particularly when the surplus tab sheets are discharged out of the apparatus, the fixing device does not perform a fixing operation, and hence the temperature of the fixing device is lowered, which requires a longer time period to achieve temperature adjustment of the fixing device for resuming printing. For these reasons, the productivity of generating printing products is lowered.
The above-mentioned temperature adjustment is executed whenever switching occurs between normal sheets and tab sheets in the print job. Therefore, it is desirable to minimize time required to discharge surplus tab sheets out of the apparatus, which is originally unnecessary for obtaining a print product for a print job.
As described above, in the conventional technique, in an image forming apparatus capable of generating print products printed by feeding different sheets from different sheet feeding cassettes, surplus sheets are discharged whenever one print product is generated. As a result, it takes time to perform temperature adjustment after the discharge of surplus sheets out of the apparatus whenever one print product in which different sheet types are mixed is generated.